Marine magnetometers are used to identify objects containing ferrous metals resting on or buried just below the surface of the seafloor. During a survey, the magnetometer records the total earth’s magnetic field along a trackline. The data are analyzed to identify anomalies (deviations from the background field) that are caused by ferrous objects.
Anomalies associated with such objects can be distinguished from other sources of magnetic disturbances which produce longer duration disturbances, such as local geological structures. Although an individual anomaly represents only the location along a trackline in which the disturbance was measured, by comparing data along adjacent tracklines and correlating with other geophysical results (i.e. side scan sonar imagery, high-resolution subbottom profiles of the very shallow subsurface) it is possible to calculate estimates of the location of the ferrous object and provide more insight about the nature of the object.